child-sa-manager: Add a global manager storing CHILD_SA relations

To quickly check out IKE_SAs and find associated CHILD_SAs, the
child_sa_manager stores relations between CHILD_SAs and IKE_SAs. It provides
CHILD_SA specific IKE_SA checkout functions wrapping the ike_sa_manager.

src/libcharon/Android.mk

@@ -72,6 +72,7 @@ sa/ike_sa.c sa/ike_sa.h \
 sa/ike_sa_id.c sa/ike_sa_id.h \
 sa/keymat.h sa/keymat.c \
 sa/ike_sa_manager.c sa/ike_sa_manager.h \
+sa/child_sa_manager.c sa/child_sa_manager.h \
 sa/task_manager.h sa/task_manager.c \
 sa/shunt_manager.c sa/shunt_manager.h \
 sa/trap_manager.c sa/trap_manager.h \
@@ -238,4 +239,3 @@ LOCAL_PRELINK_MODULE := false
 LOCAL_SHARED_LIBRARIES += libstrongswan libhydra
 
 include $(BUILD_SHARED_LIBRARY)
-